This place has infamously poor Office COM interops. In general, you should get rid of everything in the reverse order of how it was made. As an illustration, suppose that after creating Excel.Application, you also have references to workbooks and sheets. If you call. If you quit without first deleting any worksheet references and closing the workbook, the process is retained in memory. You shouldn't need to call FinalReleaseComObject; in fact, if references are still held in memory after disposal, the process may or may not crash.
I hope this helps you.